Guide Geo users to the right version of the documentation for them

The following discussion from !3116 (merged) should be addressed:

• @brodock started a discussion: (+3 comments)

  because we don't have documentation versioning yet we may need to keep SSH instructions available :/

We need to basically add a similar not like in https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/update/10.0-to-10.1.md.